In a Huffington Post interview published Tuesday, the leading Democrat said that an unnamed investor with Bain Capital, Romney's former private equity firm, told Reid in a phone conversation that Romney had not paid taxes for a decade.

Reid stood by the allegations on Thursday while speaking on the Senate floor.

"The word's out that he hasn't paid any taxes for 10 years," he said. "Let him prove he has paid taxes because he hasn't."

Democrats and President Barack Obama's re-election campaign have repeatedly called for Romney to release more tax documents to answer any questions about his financial portfolio.

Romney has made public the full 2010 tax return and an estimate for 2011, with a pledge to release the full year once it's complete. He filed an extension for an October deadline.

Critics have hit back against Reid's comments this week, faulting him for making claims based off an anonymous source.

"Harry's gonna have to describe who it is he spoke with because of course that's totally and completely wrong," Romney said Thursday in the radio interview. "It's untrue, dishonest and inaccurate. It's wrong. So I'm looking forward to have Harry reveal his sources and we'll probably find out that it's the White House."

Mirroring Romney's comments, senior campaign adviser Eric Fehrnstrom described Reid's comments as "shameful, pathetic, baseless and untrue" and argued the majority leader, with the help of the Obama campaign, was attempting to "engage in McCarthy-like accusations about Mitt Romney."

"Four years ago Barack Obama said he was going to come to Washington and change the politics. Instead the Obama campaign has turned into a bottomless pit. Every day they reach a new low," he said Thursday on CNN's "The Situation Room."

Adding on, Fehrnstrom said Romney has "never zeroed out his tax liability" and "has always paid 100% of what was owed."

After Romney's interview on Hannity's radio show, the majority leader responded in a statement and said he is not backing down from his remarks.

"As I said before, I was told by an extremely credible source that Romney has not paid taxes for ten years. People who make as much money as Romney have many tricks at their disposal to avoid paying taxes," he said.

Reid argued Romney is "hiding something" and called on the presumptive GOP nominee to release more taxes.

"When it comes to answering the legitimate questions the American people have about whether he avoided paying his fair share in taxes or why he opened a Swiss bank account, Romney has shut up. But as a presidential candidate, it’s his obligation to put up and release several years’ worth of tax returns just like nominees of both parties have done for decades," Reid said.

According to a source familiar with Reid's thinking, the majority leader, a former boxer, considers himself a political street fighter now, willing to throw a punch and get hit back big time for a cause. In this case, the cause is making sure the topic of Romney's tax returns remains in the news, and in the campaign narrative.

The source said Reid is "happy to mix it up and put this back in the news" and added the "finger waggers of the Acela corridor won't dissuade him from speaking his mind."

Reid, the source said, is unconcerned about the hits he is taking on making unsubstantiated claims, because the Democratic base is fired up. The source says they know that anecdotally. It's not an accident that Reid said this to the Huffington Post, a friendly outlet, and did so as Romney was returning from his overseas trip.

"What happened when Romney returned? The first story he has to deal with is his tax returns," the source said.

One of Romney's biggest surrogates, Sen. John McCain of Arizona, came to Romney's defense on Thursday, saying Reid may have "gone over the line."

"I've known Sen. Reid for many, many years, and occasionally he displays some rather erratic behavior," McCain said on CNN's "Anderson Cooper 360." "To accuse someone of doing something without a shred of proof–that the allegation has any substance–is really something I, frankly, don't understand."

McCain, whose 2008 presidential campaign reviewed Romney's tax records as they considered him to be the vice presidential running mate, said last month he can "personally vouch" that there was "nothing disqualifying" in the tax returns of the presumptive GOP presidential nominee.

On Thursday, he urged Reid to come "forward" with his source.

"I think politics are tough. I enjoy the give and take but I think Harry might have gone over the line," McCain said.

Later, while visiting a fruit stand with his mother in Florida, Ryan responded to the negative reaction in the room.

"Entitlement reform has unfortunately been made very partisan by partisans, and so I have gotten that kind of reaction and unfortunately it's what we come to expect because the politics of reforming entitlements has become very bitter and it's very unfortunate," he told reporters in Lakeland.

What was it the teapublicans kept saying? "Just show the birth certificate" He did. So when will Mitt show the returns. He must be guilty by Trump and Arpaio standards.

August 3, 2012 06:37 pm at 6:37 pm |

Fromhome

He is just doing what Obama did during his campaign with the birth certificate. The opposite party gets all worked up and focuses on one issue. He knows when he will release his returns, I bet it's being carefully planned. "Hey look at this hand over here and don't about worry what the other one is doing."

August 3, 2012 06:38 pm at 6:38 pm |

Jaime

"Me thinks the lady doth protest too much"
Honestly all the BS Mr Romney is raising is just an attempt to divert the attention from the reality he is hiding. Personally, Ok so he paid taxes and probably a lot of them but what did he pay in relation to what he earned? What loopholes did he use? Where does he hide his resources? What kind of character will be seen when he reveals his taxes. Sneaky, slimy, moves to distract and confuse. It won't work. America will not stand for it.

Mitt – can't release the tax infro. No matter how difficult the call for them, he cannot for what is hidden will surely cost him the election immediately, no matter that he paid, followed the law but how, to what degree, how honest?

And did we taxpayers really subsidize the expenses for the Romneys horse and did the taxpayers support the horse with tax breaks?√ Really? The nerve! The hypocrisy!

August 3, 2012 06:52 pm at 6:52 pm |

Aubiester

So why won't Obama release college transcripts or a valid birth certificate or medical records or.... What a joke!

12000000 jobs. You mean that you are going to put 12 million in your over seas bank account. You put up or shut up. Release the dam tax returns.

August 3, 2012 06:58 pm at 6:58 pm |

Robert Warner

"Weep weep, sob sob, those mean ol' democrats are picking on me again! Don't yhey (sob sob) know that I'm rich, so I get to be President? Why are they being so mean?? Wahwah sob weep...."

August 3, 2012 07:00 pm at 7:00 pm |

dirk thomas

Who in their right mind can actually give Reid any credibility or put any credence in these accusations based on "unnamed sources"–this is the same guy (Harry Reid) that hasn't even allowed our government budget to be brought up and voted upon in the Senate over 1200 days–give me a break–the guy is a disgrace–especially since he is the leader of the Senate–how sad! Clearly if he had a real and reliable source–Reid would name it. It's gutter politics–so much for the hope and change they promised.

August 3, 2012 07:03 pm at 7:03 pm |

BD70

Oh right on! McCain said there is nothing in Romney's tax returns! This is the guy who chose Palin as VP! He is also a republican. Please show the last ten years of tax returns Mitt. And McCain can explain later why Romney wasn't chosen for the ticket.

August 3, 2012 07:09 pm at 7:09 pm |

Rick in Phx

Mitt Romney could solve the problem and just release his tax returns. Obama did release his birth certificate and except for a few brain dead morons that pretty much settled it. I as an independent hope that Mitt Romney didn't pay taxes. That way maybe he can write a book and let the rest of us know how to avoid paying taxes.

August 3, 2012 07:10 pm at 7:10 pm |

Dave

Friday, August 03, 2012

The Rasmussen Reports daily Presidential Tracking Poll for Friday shows Mitt Romney attracting 47% of the vote, while President Obama earns support from 43%. Five percent (5%) prefer some other candidate, and five percent (5%) are undecided.
Republicans continue to follow the election more closely than Democrats or unaffiliated voters. This is a key indicator of potential turnout.

August 3, 2012 07:10 pm at 7:10 pm |

OBG

Is this really where the Dems are? Making accusations based on hearsay?

Naming the source and get the source fired? It is the same as Michel Bachmann saying "Someone told me their kid suffered brain damage because of vaccination." There was no screams of put up or shut up? It was simply dismissed for the baseless claim it was. And such disclosure doesn't even cause the person harm. The mother that told bachmann this would not be fired, or suffer foreseeable retaliation.

To actually have to defend in such a matter shows that the claim might not be as empty as it seems.

August 3, 2012 07:15 pm at 7:15 pm |

HughRHigh

No truth will ever come from Harry Reid. He has no shame. He is a bottom feeder. His elevator does not reach the top floor.

August 3, 2012 07:17 pm at 7:17 pm |

asm_ith

Romney challenges Reid to name sources, but then goes on himself to say that "we'll probably find out that it's the White House." So Romney should also put up or shut up as to why it is the White House. If he can't, then he has no standing to challenge Reid's speculation based on unnamed sources. If he can make accusations without evidence, then others can as well.

August 3, 2012 07:18 pm at 7:18 pm |

Glenn Rice

Sarah Palin saw the Romney tax returns in 2008. She has let it be known that Romney's returns will do more harm if released than just riding it out. How good a candidate can Mitt be when Sarah is picked ahead of him for VP?

August 3, 2012 07:21 pm at 7:21 pm |

Has Mittens "RETROACTIVELY RETIRED" as the GOVERNOR of MA back to before he signed ROMNEYCARE???

"Hate his politics? Fine... Hate his constant flip-floppery? Great... Hate his religion? You're a bigot- but whatever... But you can't honestly and in good faith criticize a guy for being successful AND savvy enough to save money where money can be saved – whether it's here or in the Cayman Islands. All of us would do exactly the same thing if we were in that same (very elegant) boat and we all know it. If you say you wouldn't then your either a liar or an idiot. Or, more likely, both"

But we would also be "savvy enough" NOT to "rock the boat" and run for the highest office in he land because our creative way to wealth maybe discovered!

August 3, 2012 07:23 pm at 7:23 pm |

Ken

It appears as though Let Them Eat Cake Mitt is actually saying to America "Kiss My A$$" – at least he isn't using one of his staffers to say so. This is such an added personal touch!

August 3, 2012 07:25 pm at 7:25 pm |

gee

Like father like son?? Guess his dad's decent example is too big a pill to swallow.

August 3, 2012 07:31 pm at 7:31 pm |

mirrorlogic

How many people know that Romney had a similar scandal when getting qualified to run for Gov in Mass. He had taxes going to Utah that saved him money, then found out he needed to be a Mass resident all that time, so when asked about it, as usual he explained it was an error someone else did – he didn't know such things. he had the forms revised to make him eligible. Funny how he also doesn't know what those kinds of things...etc, etc, etc